MAS-NMR is a powerful tool for determining chemical speciation in mixed phase samples. MAS-NMR performed at conditions of combined high temperature and high pressure has not been realized for a number of reasons, leaving the monitoring of chemical reactions and transformations in situ largely unexplored. Various attempts have been made to create modifications to MAS-NMR designs to attempt to address these limitations.
One previous rotor design included a ceramic zirconia rotor configured with polymer bushings made of TORLON® that were secured to narrow threads positioned along the inner wall of the rotor cylinder using an epoxy adhesive. This design worked well for samples examined at lower temperatures and pressures and mild reaction conditions such as those involving methane in carbon dioxide. However, in harsh sample conditions the epoxy adhesives break down in the rotor. Sealing devices used in these rotors can also fail. Previous designs also frequently required specialized pressure loading devices to load gases into the rotor at elevated pressure conditions. Thus, these prior art rotor cylinder designs are generally not suitable for in-operando monitoring of samples undergoing reactions at combined pressures above 200 bar and temperatures above 80° C.
Due to limitations in current rotor designs, many chemical systems have not been examined and characterized by MAS-NMR. Accordingly, new bushing designs and methods are needed for sealing sample chambers in rotors without adhesives that enable operation at combined high temperature and high pressure conditions. The present invention addresses these needs.